Under-reamer



March 24, 1959 c. F. JOHNSON 2,879,038

UNDER-REAMER Filed Oct. 28, 1957 lN-VENTOR ATTORNEY United States PatentUNDER-REAMER Chester F. Johnson, Los Angeles, Calif.

Application October 28, 1957, Serial No. 692,677

Claims. (Cl. 255-76) This invention relates to under-reamers of the typeemployed in forming channels in bores produced in walls fabricated ofconcrete, brick, stone and the like for the reception of expansion boltsemployed in the attachment of structures to the walls.

An object of the invention is to provide an underreamer of the abovecharacter embodying a shank for engagement with a power driven rotarychuck, in which the shank is equipped with under-reaming cutters mountedfor movement in and out of an under-reaming position and in which meansare provided for actuating the cutters through rotation of the shankadapted to advance the cutters on rotation of the shank in one directionand to retract the cutters on reversing the rotation of the shank.

A particular object is to provide yieldable resilient means interposedbetween the shank and cutters for actuating the latter such as toobviate sudden impact on the cutters as might cause the latter toexcessively dig into the wall being cut and thereby stall the motivepower or damage the cutters or their mountings.

Another object is to provide a simple and effective means for cushioningoperation of the cutters.

Another object is to provide a construction in the under-reaming cuttersand a mounting therefor such that the cutters may be readily removed andreplaced and whereby the cutters may be so economically constructed asto render them expendible; the cutters being designed to be sharpenedwhen slightly worn and to be discarded and replace when excessivelyWorn.

A further object is to provide an under cutter of the above charactercomprising few simple parts that may be readily manufactured andassembled.

With the foregoing objects in view together with such other objects andadvantages as may subsequently appear, the invention resides in theparts and in the combination, construction and arrangement of partshereinafter described and claimed, and as illustrated by Way of examplein the accompanying drawing in which:

Fig. l is a view of the under-reamer as seen in side elevation; v

Fig. 2 is a horizontal section and plan view as seen on the line 2-2 ofFig. 1 showing the under-reamer cutters v continuous screw threads 6 onits outer end portion on which is loosely screwed an internally threadedcylindrical sleeve 7 having a fiat inner end 8 extending perpendicularto the axis of the shank A. The shank A has a reduced diameter portion 9at the inner end of the threads 6 which reduced diameter portion hasextending therethrough a diametrical slot 10 in which is mounted a platespring 11 comprising a normally straight strip of flat stiff butresilient metal having a thickness slightly less than the width of theslot 10 so as to permit lateral but limited movement of the spring 11 inthe slot 10. The end margins of the side wall of the slot 10 are roundedas indicated at 12.

Projecting from the flat end face of the sleeve 7 is a pair ofcylindrical pivot pins 1414 disposed on diametrically opposite sides ofthe shank A on radii extending at an angle clock-wise relative to radiiextending perpendicular to the slot 10. Mounted on the pivot pins 1+-14is a pair of end-to-end under-reaming cutters BB particularly shown inFig. 5 each of which cutters comprises an arcuate flat sided arm 15having an arcuate inner margin 16 normally in spaced relation to thereduced diameter portion 9 of the shank A and having an arcuate outermargin 17 normally lying inwardly of the outer margin of the sleeve 7 onthe flat end faces 8 of which the arm B slidably seats. The outer margin17 of each of the arms B converges toward the inner margin 16 along thelength of the arm between the point of engagement of the arm with thepivot pin 14-14 to a point adjacent but spaced from the outer end of thearm, which convergent portion 18 terminates in an outwardly projectingunder-reaming tooth 19 presented toward the pivot pin 1414. The pivotalconnection between the arm B and pivot pin is located adjacent to butspaced from the inner end 20 of the arm which inner end is designed toabut at its juncture 20 with the margin 16 with the reduced diameterportion 9 when the arm is swung outwardly to its fully extended positionshown in Fig. 4. The inner margin of each of the arms BB has an openended slot 21 located adjacent the outer end of the arm with which slotsthe outer ends of the spring 11 are slidably and normally looselyengaged as shown in Fig. 2.

Mounted on the shank A at the inner end of the reduced diameter portion9 is an adjustable collar 22 for limiting advance of the sleeve 7 on thethreads 6, the collar 22 being adapted to be positioned adjacent to theouter ends of the pivot pins 1414 to afford an abutment therefor andalso serve to hold the under-reamer arms B against displacementlongitudinally of the shank A, which arms have a thickness slightly lessthan the length of the pivot pins so as to afford a clearance betweenthe arms B and the adjacent flat face of the collar 22. As a means forfacilitating adjustment of the collar 22 longitudinally of the shank A,which is necessary in order to permit assem blage of the spring 11 inthe slot 10, the shank A is formed with screw threads 23 leading fromthe inner end of the reduced diameter portion 9 on which threads 23 thecollar 22 is screwed. On rotating the collar 22 it may be advanced orretracted on the threads 23.

In assembling the parts of the under-reamer, collar 22 is initiallyscrewed on the shank A over the threads 6 which correspond to thethreads 23, and is then screwed onto the latter to a retracted positionas indicated by the dotted lines a in Fig. 3. The sleeve 7 is thenscrewed onto the threads 6 until the flat end face 8 of the sleeve isaligned with the outer end margin of the slot 10. One of the arms B isthen engaged with one of the pivot pins 14 by positioning the inner endportion of the arm over the pin then manipulating the arm to pass acylindrical opening 24 therein over the pin so as to seat the arm on thefiat end face of the sleeve. The spring 11'is then inserted in the slot10 from the side of the shank opposite the assembled arm B and itsadvancing end is passed through the slot 10 and projected into the slot21 of the assembled arm B. The other arm B is then assembled in likefashion on the other pivot pin 14 and in so doing is manipulated toengage the slot 21 of such arm with the other end of the spring 11 thenprojecting from the shank A. The assemblage will then appear as shown inFig. 2 with the arms BB seated on the adjacent fiat end face 8 of thesleeve 7 and with :the upper ends of the pins 14 projecting slightlyabove the adjacent faces of the arms BB and slightly above the plane ofthe upper margin of the spring 11. The collar 22 is then advanced on thethreads 23 and brought into slightly spaced relation to the upper endsof the pins 1414 thus completing the assemblage.

In the operation of the invention, the shank A is engaged in a powerdriven rotary chuck in a usual fashion, whereupon the under-reamer withthe arms BB re- .tracted as shown in Figs. 1 and 2 is inserted in a boreto be reamed which bore has a diameter slightly larger than the diameterof the sleeve 7 so as to slidably receive the sleeve 7. On thusdisposing the under-reamer in the desired position in the wall bore, theshank A is rotated.

The sleeve 7 being loosely engaged by the threads 6 of the shank,initial turning movement of the latter which ,is sudden and swift willoccur for an instant independent of the sleeve 7 such as to cause theends of the spring 11, carried by and advancing with the shank A, toexert an outward thrust on the arms BB such as to bring theunder-reaming teeth 19 thereon into contact with the surfaces of thewall bore thereby imposing a drag on the sleeve 7 tending to initiallyresist rotation of the sleeve until such resistance is overcome by thethrust of the end portions of the spring 11 against the side wall of theslots 21 against which the outer ends of the spring .11 bear. When thisoccurs the sleeve 7 will rotate at least substantially in unison withthe shank A and at the same time the end portions of the spring 11 willexert .an outward thrust on the arms BB and thereby cause .theunder-reaming teeth 19 to effect cutting engagement with the surface ofthe wall bore such as to effect a cutting action thereon and therebyform a channel around the wall bore.

Initial thrusts of the ends of the spring 11 on the arms BB in forcingthe latter outward are cushioned since the spring will yield inopposition to its tension under resistance offered to outward movementof the arms when the teeth abut the surface of the wall bore. Thisaction coupled with outward movement of the arms being under springpressure minimizes possibility of stalling of the motor utilized indriving the under-reamer.

Outward movement of the arms BB is limited by the inner end portions 20of the arms being brought into abutting engagement with thediametrically reduced portion 9 of the shank A under the thrust of theend portions of the spring 11 as shown in Fig. 4.

Back pressure imposed on the .ends of the spring 11 during their forwardmovement relative to the arms BB flexes the spring as illustrated inFig. 4 thereby placing it under tension such that on cessation of thedriving ,force and/or slight retrograde turning of the shank A thespring will return to its normal straight condition thereby causing theopposite ends of the spring 11 toride into the slots 21 and engage theouter side walls of the latter such as to effect retraction of the armsBB to their normal position shown in Fig. 2 whereupon the under-reamermay be withdrawn from the wall bore. This retraction of the arms isfacilitated by reason of the wall of the slots 21 then engaged by theends of the spring 11 extending in such angular relation to the springas to present upwardly inclined planes to the advancing ends of thespring so that the latter will exert a wedge action such as to draw theouter ends of the arms BB inwardly.

In event it becomes necessary to remove the under- Iearner arms BB forsharpening or replacement, such maybe. readily accomplished byretracting the collar 22 on the threaded portion 23 so as to permitlifting of the arms BB from the pivot pins 1414 and thusfreeing the armsfrom engagement by the end portions of the spring 11.

While I have shown and described a specific embodiment of the invention,I do not limit myself to the exact details of construction set forth,and the invention em braces such changes, modifications and equivalentsof the parts and their formation and arrangement as come within thepurview of the appended claims.

I claim:

1. In an under-reamer, a shank having continuous screw threads on an endportion thereof and a reduced diameter portion at the inner end of saidscrew threads, and having a slot extending diametrically through saidreduced portion, a cylindrical sleeve loosely screwed on said threadsfor free rotation relative to said shank, said sleeve having a flat endpresented to said reduced portion of said shank, a pair of end-to-endarcuate arms pivoted on said fiat end for swinging movement laterally ofsaid shank and sleeve, an outwardly extending under-reaming tooth on theouter end portion of each of said arms arranged to overlie said flat endwithin the margins thereof when said arms are in their innermostpositions, actu ating means carried in said slot engaged with said armsoperable on rotating said shank relative to said sleeve to swing saidarms out and in relation to said shank and sleeve, and means on saidshaft limiting advance movement of said sleeve on said threads.

2. The structure called for in claim 1 in which said actuating meanscomprises a metallic strip having end portions protruding from said slotslidably engaging the inner margin of theouter end portions of saidarms, said strip being stiff yet yieldable and resilient.

4. The structure called for in claim 1 in which said actuating meanscomprises a metallic strip having end portions protruding from said slotslidably engaging the inner margin of the outer end portions of saidarms, said strip being stiff yet yieldable and resilient and said armseach having a slot on its inner margin into which an end of said stripextends.

5. In an under-reamer, a shank having screw threads on an end portionthereof and a reduced diameter portion at the inner end of said threadsand having a slot extending diametrically through said reduced portion,a cylindrical sleeve loosely screwed on said threads for free rotationalmovement thereon, said sleeve having a flat end presented to saidreduced portion, a pair of diametrically opposed pivot pins projectingfrom said flat end, a pair of end-to-end arcuate arms pivoted on saidpins for swinging movement laterally of said shank and sleeve, anoutwardly projecting under-reaming tooth on the outer end portion ofeach of said arms arranged to overlie said flat end within the marginsthereof when said arms are in their innermost retracted positions andadapted to project laterally from the outer margin of said sleeve whensaid arms are in an advanced position, a plate spring in said slothaving its ends projecting laterally from opposite sides of said shankand slidably engaged with the outer end portions of said arms foradvancing and retracting said arms on turning said shank and sleeverelative to each other, and a collar adjustably mounted on said shank atthe inner end of said reduced portion for seating on the outer ends ofsaid pivot pins to thereby retain said arms and said plate spring intheir assembled position on said shank and sleeve.

6. In an under-reamer, a shank, a sleeve loosely threaded on said shankand having an inner end, a pair of arms pivoted on said inner end eachhaving an underreaming tooth projecting outwardly from the outer endportion of the arm, stiff but resiliently yieldable projections onsaidshank slidably engaging said arms for advancing and retracting saidarms on relative rotation of said shank and sleeve, and means on saidshank limiting advance movement of said sleeve relative to said shank.

7. In an under-reamer, a shank having a slot extending therethroughhaving opposed side walls, a sleeve loosely threaded on said shankhaving an inner end, a pair of arms pivoted on said inner end eachhaving an under-reaming tooth projecting outwardly from the outer endportion of the arm, stiff but resiliently yieldable projections on saidshank slidably engaging said arms for advancing and retracting said armson relative rotation of said shank and sleeve; said projectionscomprising the end portions of a plate spring carried by said shankextending between the side walls of said slot and adapted to bear oneither of said side walls according to the direction of rotation of saidshank and sleeve relative to each other, and means on said shanklimiting advance movement of said sleeve relative to said shank.

8. In an under-reamer, a shank having screw threads on an end portionthereof and a reduced diameter portion at the inner end of said threads,a cylindrical sleeve loosely screwed on said threads for free rotatablemovement on said shank, said sleeve having a flat end presented to saidreduced portion, a pair of end-to-end arcuate arms pivoted at theirinner ends on said flat end for swinging movement laterally of saidshank and sleeve, an outwardly extending under-reaming tooth on theouter end portion of each of said arms arranged to overlie said fiat endwithin the margins thereof when said arms are in their innermostpositions and adapted to project laterally from the outer margin of saidsleeve into under-reaming position when said arms are swung outwardlyrelative to said shank, means carried by said shank engaged with saidarms operable on rotating said shank relative to said sleeve to swingsaid arms out and in relative to said shank and sleeve, and means onsaid shank limiting advance movement of said sleeve on said threads.

9. In an under-reamer, a shank having screw threads i on an end portionthereof and a reduced diameter portion at the inner end of said threads,a cylindrical sleeve loosely screwed on said threads for free rotatablemovement on said shank, said sleeve having a fiat end presented to saidreduced portion, a pair of end-to-end arcuate arms pivoted at theirinner ends on said flat end for swinging movement laterally of saidshank and sleeve, an outwardly extending under-reaming tooth on theouter end portion of each of said arms arranged to overlie said fiat endwithin the margins thereof when said arms are in their innermostpositions and adapted to project laterally from the outer margin of saidsleeve into underreaming position when said arms are swung outwardlyrelative to said shank, yieldable tensioned means carried on said shankand engaged with said arms operable on turning said shank relative tosaid sleeve to advance and retract the outer end portions of said armsrelative to said shank and sleeve, and means on said shank limitingadvance movement of said sleeve on said threads.

10. In an under-reamer, a shank having a diametrical slot adjacent oneend thereof, an abutment collar screwed on said shank adjacent the innermargin of said slot, a cylindrical sleeve loosely threaded on said shankat the outer margin of said slot for free rotation relative to saidshank; a pair of under-reamer arms pivoted on the inner end of saidsleeve, a plate spring extending through said slot having its endsslidably engaged with said arms and adapted to swing said arms onturning said shank relative to said sleeve, and pivot pins on saidsleeve carrying said arms having outer ends presented to said collar andadapted to abut the latter to then limit advance move ment of saidsleeve on said shank and also serve to retain said arms on said pins.

Newell Sept. 2, 1902 Berkman Nov. 8, 1938

